Nasa's Laser Helping Gauge Air

October 02, 2006|By JIM HODGES, jhodges@dailypress.com | 247-4633

HAMPTON — With an eye on the future, NASA Langley scientists measure particles in the present.

The Learjet gained altitude quickly, going to 20,000 feet and flying at 400 knots from Newport News/ Williamsburg International Airport, south to Chesapeake's Dismal Swamp and then east over Virginia Beach and the Atlantic before turning back, passing over Yorktown and finally touching down.

On board, an instrument known as LIDAR -- for "light detection and ranging" -- sent out 20 laser beam pulses per second and measured their interruption en route to Earth and their return to the jet. Those interruptions are what we breathe -- aerosols emitted from tailpipes and smokestacks -- mixed in with the air that keeps us alive.

It was a $6,500, one-hour investment in the future.

"People are getting more sensitive to health effects and more concerned about their health," said Russell De Young, an assistant branch head in the science directorate at NASA Langley Research Center.

"They're asking questions: 'What's the air quality like and should I be paying attention to it so that I can protect my health?' We're trying to understand how aerosols are generated and how they are transported. That's the big issue, how are they transported?"

Aerosols are tiny particles in the air that can impede respiration and the cardiovascular system.

During the recent flight, the air was clear and aerosols fairly hard to find in bulk when the Learjet was aloft. On Aug. 4, the day after the plane's previous trip on a similar quest, the Daily Press carried the headline: "Area's bad air days increase particle pollution."

Finding concentrations of aerosols then was no problem. The scientists at NASA Langley learned how bad those air days really were.

"It was the worst we've ever seen it," De Young said.

People rubbing their eyes or struggling to breathe on the Peninsula that day understood.

Evidence is reflected in a computer graphic of a ribbon of colors from light purple to black, with the darkest color showing the greatest collection of aerosols at about 6,000 feet, stretching over Hampton Roads and miles into the Atlantic Ocean. It's called the boundary layer, a sort of ceiling over the area caused by wind currents that you feel when you're landing in a plane and blaming the pilot for being bounced around.

Aerosols are generated on the ground and are carried up with warm air to gather at the boundary layer, then seeping through into the atmosphere. There, they can join with other aerosols that are blown into the area and that are heavy enough to go back down into noses and lungs.

Measuring aerosols is an evolving process that is becoming more important with urban development. Tracking them is part of a future that will help identify their source.

It begins in space with satellites, but their broad-brush pictures need help a bit closer to Earth to be more useful. That's where ground LIDAR from NASA Langley and the Chesapeake Lighthouse come into play, along with the flying LIDAR from the Learjet.

"The satellite looks at this large area, then we go in with a scalpel," De Young said. "We can pinpoint where the aerosols are, both vertically and horizontally.

"That's very important to know, because aerosols are generated in a metropolitan area, but sometimes they come from Washington, D.C., or a forest fire in Canada or in the South."

Determining their origin is the job of the satellite. Determining their impact involves the closer scrutiny of airborne or ground LIDAR and of stations like that at the Virginia School for the Deaf, Blind and Multidisabled in Hampton that suck in air to measure its contents.

And even after their region of origin is found, the question arises about what can be done to control aerosols.

"How do you separate man-made aerosols from natural aerosols," De Young asks rhetorically. "The wind's going to pick up dust, no matter where you are."

It's a question still being answered by local flights along with satellites such as CALIPSO -- or Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation -- which is also a NASA Langley project.

And by a flight scheduled for later in the year or early in 2007 to California's Central Valley, where aerosols gather in eye-blurring bulk from effluence blown down the valley from the San Francisco Bay area and from dust churned up in agriculture. It gathers at the Tehachapi Mountains, and NASA Langley is excited about the prospect of measuring the aerosols there.

"The problem with the Central Valley is that it's a bowl and there's nowhere for the aerosols to go," De Young said. "Here, we're lucky. There's an ocean and, if they go out over the ocean, poof, they're gone."

Except on days like Aug. 3.

Using the data is also still an evolving process. The Environmental Protection Agency helps fund it, and others who will determine development will use it.

But its value is still somewhat futuristic.

"As we get more data, we understand better what the atmosphere is doing," said De Young. "In order to have good public policy, you have to do the science first. This is the science you do before you have meaningful public policy." *